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      D-dimer levels and cerebral infarction in critically ill cancer patients.

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          Abstract

          D-dimer levels have been used in the diagnosis of a variety of thrombosis-related diseases. In this study, we evaluated whether measuring D-dimer levels can help to diagnose cerebral infarction (CI) in critically ill cancer patients.

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          Youden Index and optimal cut-point estimated from observations affected by a lower limit of detection.

          Marcus Ruopp, Neil J Perkins, Brian W Whitcomb … (2008)
          The receiver operating characteristic (ROC) curve is used to evaluate a biomarker's ability for classifying disease status. The Youden Index (J), the maximum potential effectiveness of a biomarker, is a common summary measure of the ROC curve. In biomarker development, levels may be unquantifiable below a limit of detection (LOD) and missing from the overall dataset. Disregarding these observations may negatively bias the ROC curve and thus J. Several correction methods have been suggested for mean estimation and testing; however, little has been written about the ROC curve or its summary measures. We adapt non-parametric (empirical) and semi-parametric (ROC-GLM [generalized linear model]) methods and propose parametric methods (maximum likelihood (ML)) to estimate J and the optimal cut-point (c *) for a biomarker affected by a LOD. We develop unbiased estimators of J and c * via ML for normally and gamma distributed biomarkers. Alpha level confidence intervals are proposed using delta and bootstrap methods for the ML, semi-parametric, and non-parametric approaches respectively. Simulation studies are conducted over a range of distributional scenarios and sample sizes evaluating estimators' bias, root-mean square error, and coverage probability; the average bias was less than one percent for ML and GLM methods across scenarios and decreases with increased sample size. An example using polychlorinated biphenyl levels to classify women with and without endometriosis illustrates the potential benefits of these methods. We address the limitations and usefulness of each method in order to give researchers guidance in constructing appropriate estimates of biomarkers' true discriminating capabilities. Copyright 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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            Optimal cut-point and its corresponding Youden Index to discriminate individuals using pooled blood samples.

            Stephen J. Perkins, Aiyi Liu, Howard Bondell … (2004)
            Costs can hamper the evaluation of the effectiveness of new biomarkers. Analysis of smaller numbers of pooled specimens has been shown to be a useful cost-cutting technique. The Youden index (J), a function of sensitivity (q) and specificity (p), is a commonly used measure of overall diagnostic effectiveness. More importantly, J is the maximum vertical distance or difference between the ROC curve and the diagonal or chance line; it occurs at the cut-point that optimizes the biomarker's differentiating ability when equal weight is given to sensitivity and specificity. Using the additive property of the gamma and normal distributions, we present a method to estimate the Youden index and the optimal cut-point, and extend its applications to pooled samples. We study the effect of pooling when only a fixed number of individuals are available for testing, and pooling is carried out to save on the number of assays. We measure loss of information by the change in root mean squared error of the estimates of the optimal cut-point and the Youden index, and we study the extent of this loss via a simulation study. In conclusion, pooling can result in a substantial cost reduction while preserving the effectiveness of estimators, especially when the pool size is not very large.
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              Stroke and cancer: the importance of cancer-associated hypercoagulation as a possible stroke etiology.

              Christopher Schwarzbach, Anke Schaefer, Anne D. Ebert … (2012)
              The importance of cancer-associated hypercoagulability as a possible stroke etiology in patients with cancer has received relatively little attention to date. A recent study has suggested that cancer-associated hypercoagulation may be of special importance in the absence of conventional stroke mechanisms.
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                Author and article information

                Journal
                Journal ID (iso-abbrev): BMC Cancer
                Title: BMC cancer
                Publisher: Springer Science and Business Media LLC
                ISSN (Electronic): 1471-2407
                ISSN (Print): 1471-2407
                Publication date (Electronic): Aug 30 2017
                Volume: 17
                Issue: 1
                Affiliations
                [1 ] Department of Critical Care Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 135-710, Republic of Korea.
                [2 ] Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 135-710, Republic of Korea.
                [3 ] Department of Neurology, Dankook University College of Medicine, Anseo-dong San 16-5, Cheonan-si, Chungcheongnam-do, 330-715, Republic of Korea. lamyud9@gmail.com.
                Article
                Publisher Item ID: 10.1186/s12885-017-3588-7
                DOI: 10.1186/s12885-017-3588-7
                PMC ID: 5576032
                PubMed ID: 28854911
                SO-VID: 5a8a691c-99dd-4d63-92ed-ac9d1ffa788a
                History

                Keywords: Brain magnetic resonance imaging,Cancer,Cerebral infarction,D-dimer,Intensive care unit
                Data availability:
                Keywords: Brain magnetic resonance imaging, Cancer, Cerebral infarction, D-dimer, Intensive care unit

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